A typical spindle-type cotton picker includes upright cotton picker drums with bars or columns of rotating spindles that engage the cotton plants. The drums are rotated so the rearward motion of the spindles in the picking zone is synchronized to the forward speed of the picker to generally obtain zero relative velocity between the cotton plant and the spindles engaging that cotton plant.
The picker drums present a large mass in motion with numerous rotating parts and therefore have a limited rotational speed. The drum speed limitation dictates the maximum harvest speed of the picker. Attempts to increase picker speed have concentrated on reduction of drum mass, better lubrication of the rotating elements that experience increased friction with increased speed, and minimization of acceleration of mass as the columns of spindles are oriented by a by picker bar cam arm and a cam track.
Previously available row units using the drum circumferential speed to achieve the synchronization also included a cam track that angularly positioned the spindles to move the tips of the spindles closer in the picking zone. This angular positioning of the spindles increased the spindle density in the picking zone but actually compromised spindle/plant synchronization in the zone since the effect of decreasing spacing was to slow the rearward speed of spindles in the zone. The spindle tips moved more slowly than their bases generally throughout the entire picking zone, and in an aft portion of the zone the spindle tip velocity decreased even more. Therefore, forward harvester speed was limited by the slowing of the spindles in the picking zone.